SEOUL, March 10 -- Google's computer program AlphaGo on Thursday started off with anomalies in the second Go match with human opponent South Korean Lee Sedol, the world champion of the ancient Chinese board game.

Lee and AlphaGo started the second of a historic five-game match at about 1 p.m. (0400 GMT) at Four Seasons hotel in Seoul. The landmark fight between a human and artificial intelligence (AI) will run until next Tuesday.

Playing Black, the computer program put its starter at the upper-right flower spot. In turn, Lee also placed his first white marker at a flower.

About one and a half minutes later, AlphaGo put the third marker at a position right beside the flower spot, an unconventional move different from the previous day's strategy. AlphaGo placed its first two pieces on the flower spots on Wednesday.

Exchanging conventional moves with each other, AlphaGo put its 13th marker at an anomalous position in the middle of the upper board, which a commentator said was a move he had never seen in the human world of the game.

Another commentator said it may take more than the previous day for the second game to close to an end as the two players are playing in a relative conventional manner.

AlphaGo beat the human Go champion, who has topped the world ranking for most of the past 10 years, during the first face-off of the historic match, which is seen as a representative battle between humans and artificial intelligence.

Lee's loss was seen as a shock as it proves that AI may have surpassed humans in Go, which had been viewed as the last game humans can dominate over machine due to its complex, creative and intuitive nature.

AlphaGo is a computer program developed by Google's London-based AI subsidiary DeepMind. It took the world by surprise after beating European Go champion Fan Hui by 5-0 in October last year.

The AI boasts of a deep learning capability that enables the computer program to discover new strategies by playing games against itself and adjusting neural networks based on a trial-and-error process known as reinforcement learning.

Lee, 33, is seen as one of the greatest Go players in the world as he won 18 world championships for 21 years of his professional career. He recorded a winning rate of about 70 percent with 47 victories in professional matches, while AlphaGo posted a 99.8 percent rate with 504 victories and only one defeat.

Go originated from China more than 2,500 years ago. It involves two players who take turns putting markers on a grid-shaped board to gain more areas on it. One can occupy the markers of the opponent by surrounding the pieces of the other.